Dietary protein content alters both male and female contributions to Drosophila melanogaster female post-mating response traits

Males transfer sperm, proteins and other molecules to females during mating. In Drosophila melanogaster, these molecules contribute to the induction of egg maturation, ovulation, oviposition, sperm storage and changes in female receptivity. This suite of physiological and behavioral changes is referred to as the female post-mating response (PMR). Protein is a necessary macronutrient for both male and female reproduction, but imbalances in protein content can decrease reproductive potential. Dietary protein affects the production of proteins in the male ejaculate that are important for induction of the PMR, and female fecundity increases with dietary protein while lifetime mating rate decreases. The effects of dietary protein levels on other aspects of the female PMR and on male ability to induce the PMR are unknown. To investigate how protein content affects PMR, we raised flies on diets containing low, moderate or high levels of protein and mated females and males from each diet in a combinatorial manner. We first measured the mating duration for each pair, an indication of male reproductive investment, and then evaluated two aspects of the female PMR, fecundity and female remating latency. We found that mating duration was negatively correlated with male dietary protein, and females that mated with high protein males laid fewer eggs. Female diet had no effect on mating duration, but females fed diets with higher protein content laid more eggs and remated sooner. Therefore, dietary protein levels can affect postcopulatory processes important for reproductive output in a sexually dimorphic manner.